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Thread: Ham's '48: Timken Rear Axle Vent

  1. #1
    Super Moderator LarrBeard's Avatar
    Join Date
    Nov 2014
    Ft. Wayne, IN

    Ham's '48: Timken Rear Axle Vent

    After 60+ years with this truck you'd think it had done just about everything it could to surprise me, but a couple of days ago it found a new trick.

    We had one of those fake spring days here in NE Indiana so I took the truck out for a run after I did a couple of things that had been waiting on warmer weather.

    I had also cleaned out the "car barn" to get rid of winter stuff so I had a nice clean floor for a change. I pulled the truck into the barn and it piddled on the nice clean floor. It was differential lube and my first thought was"Oh my goodness, I have a leaking pinion seal" - or words to that effect. So, I cleaned up the mess and crawled up under the rear axle and saw that the leak was coming from the top of the driver's side axle.

    There is a vent there and differential lube was blowing out through that vent. No, its never done that before and no, I haven't added any lube to the differential over the winter. I was able to unscrew the vent and it seems to be OK as far as I can tell - just a little threaded fitting and a nipple with a loose cap on it. There is no sign of any kind of spring or check valve action in it.

    I know there is a vent on front differentials on the CJ's, probably one on the Dana rear axles. Is there any secret to how they work; springs or such?

    I put it back together and when I get back to it I am going to drain the differential and see just how much lube there is in there. It's not making any noises or acting up - but I wonder why it's throwing that much lube around all of a sudden and losing it through the vent?

    Any ideas?

  2. #2
    Super Moderator bmorgil's Avatar
    Join Date
    Dec 2018
    Northwestern Ohio
    No secret LarrBeard. Just as you suspected a 1/8" pipe thread plug with a cap loosely stamped on it. When we sold axles to Jeep in the latter years, that vent was almost always attached to a hose and directed up to the body so water fording would not invade the axle. It is a very good idea to duplicate that. When I worked with the off road guy's that mod is mandatory. The only time I remember issues like this with our axles was after high RPM usage or, if the vehicle sat significantly inclined to the side allowing lube to fill the tube. The pressure produced in the axle is really more atmospheric than anything. The vent helps relive pressure on assembly. Like when you push in the axle shaft on the sealed unit. It never should come into play. Somehow that tube got filed and the shaft slung the lube against the vent. The axle shafts are so rough they do throw a lot of oil.

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